Applied Mechanics and Materials Vols. 263-266

Abstract: In order to study the feasibility of linear Multiple User Detection (MUD) used in multi-objective spread spectrum TT&C, mathematical models of Decorrelation Algorithm (DEC) and Minimum Mean Square Error Algorithm (MMSE) are built. Simulation framework based on Simulink is given. Two algorithms are compared with traditional single user detector. The results of simulation show the two linear MUDs are better than traditional single user detection.

Abstract: An equation is put forward to calculate the temporal diffraction intensity distribution of a chirped femtosecond laser pulse when it incites a circle aperture. In the aperture central direction an analytic expression is given to calculate the temporal intensity distribution. Many factors such as the width of the laser pulse, the radius of the circle aperture, the Fresnel number at central frequency, time and the chirped coefficient of the laser pulse affect the temporal intensity. Number calculation shows that if the width of laser pulse is within a few tens of femtoseconds and Fresnel number at central frequency is much than twenty, the temporal diffraction intensity outline is not a Gaussian curve. While when the Fresnel number is less than ten and the chirped coefficient is small, the temporal intensity is an approximate Gaussian curve. If the chirped coefficient is large, the temporal intensity is not Gaussian distribution.

Abstract: This passage proposes a new method to detect mosaic not only using the Y (luminance) component in YUV color space of videos, but also using the U (chrominance) and V component. The mosaic effect is measured by the boundary pixel difference from the neighbor macroblock. Instead of detecting the existence and position of mosaic blocks as traditional methods do, this method focuses on the statistics of the number of suspected mosaic blocks so that the quality of the whole frame affected by mosaic can be assessed. Experimental results show that the new method has good performance on fallout ratio, omission factor and computational complexity.

Abstract: Ultrasonic method for the investigation of multi-layered laminates such as glass fiber reinforced plastics (GFRP) has been a challenging task in industry due to their inherent nature as a combination of constituents and the respective fabrication process. The coarse-grain structure of the material, fiber orientation and stacking sequence of laminated composites generate undesirable echoes for the ultrasonic signals during the testing. These echoes distributed randomly in time affects the measurements of ultrasonic parameters. In this paper, the utilization of attenuation and time-of-flight (TOF) of ultrasound signals to reconstruct the internal structure of GFRP subsurface region were investigated. Comparisons of these two methods were conducted on two sets of GFRP with different structure condition. Analysis of C-scan images constructed by amplitude and TOF were conducted in a two dimensional region map of the scanning profile. Experimental results showed that attenuation of amplitude gave a better indication of damage and successfully improved the defect region detection in multi-layered reinforced composite materials.

Abstract: A capacity loss tester for no-load and with-load testing of power transformer has been developed. The tester has the ability of sampling the three-phase voltage and current simultaneously. Programmable counter array (PCA) unit in MPU, which captures zero-crossing of signal by the function of positive and negative edge trigger, is applied to the average phase detection of zero-crossing in bi-direction, in order to acquire the phase difference and period accurately. In terms of software, synchronism sampling method based on real-time parameter self-optimizing is adopted to minimize period truncation error, and the measuring accuracy is improved. The capacity of the power transformer is discriminated by table-look-up method in software, corresponding to different load loss. The testing result is converted from the value under testing temperature to the value under the condition of reference temperature (75°C).

Abstract: An AGPS (assisted global positioning system) positioning method was researched with polynomial approximation in this paper. Linear positioning errors were found through the analysis of an AGPS positioning algorithm with mobile station (MS) clock error. These errors were engendered to induce a bias of reference moment. The value of an objective function can be quadratically related to the deviation of reference time. Thus, the objective function curve was fitted with three reference time values, and the lowest point of curve to amend the reference time is determined. This method can eliminate linear positioning error.

Abstract: Rapid development of wind power generation and increasing growth of installed capacity of wind turbines make it necessary to study the power quality in wind farms. To monitoring the power quality in wind farms automatically and in real time, this paper presents a remote monitoring system for power quality based on LabVIEW software and Internet technology. The remote panel technology in LabVIEW and the Browser/Client (B/S) mode are adopted. This system mainly consists of monitoring hardware devices, the server, LabVIEW application software and remote clients. In the system, the remote clients in monitoring center workstations can monitor in real time power quality parameters of each wind turbine in wind farms through the VI control panel in the Internet browser. Thus it enables to improve automation level of wind farms and reduce operation and maintenance cost. The feasibility and coordination of the developed system are validated by experimental simulating results in the laboratory environment.

Abstract: Based on hydraulic sensors and wireless transmission, a new wireless measurement method of liquid volume in a tank is introduced. This measurement system includes hydraulic pressure sensors, A/D converter, GPRS (General Packet Radio Service) module and upper monitor in a computer, from which the users can get aware of the liquid volume in a tank at any time. The measurement system has been built，calibrated and tested. The experimental results show that this measurement system works well and the measurement error is less than 1%.

Abstract: Operating condition recognition of ball mill load is important to improve product quality, decrease energy consumption and ensure the safety of grinding process. A probabilistic one-against-one (OAO) multi-classification method using partial least square-based extreme learning machine algorithm (PLS-ELM) is proposed to identify the operating state of ball mill. The feature of shell vibration spectrum is extracted using KPCA. PLS-ELM model is applied to enhance the reliability and accuracy of the operating conditions identification of the ball mill load. Posterior probability of each class using Bayesian decision theory is defined as a measure as classification reliability. Classification results of the experimental ball mill shown that the accuracy and stability of the proposed method outperform ELM, PLS-ELM and KPCA-ELM model.

Abstract: Embedded devices are confined to be agents although they have been deployed in network management system for decades. We shed light on this situation by designing and implementing a new full-featured embedded network management system. On one hand, this system can still be an agent; on the other hand, this system provides a friendly GUI and I/O devices such as mouse and keyboard, which allows administrators to conveniently monitor and configure the managed equipment. The new system is developed on ARM with Linux using multithreading method, and it is deployed on ROADM equipment in optical network. SNMP is applied to be the network management protocol.